The present invention relates generally to devices which clean debris, dust and other particulate matter from filtering units. More particularly, the present invention relates to a pneumatic device used to individually clean filter cages and filter bags used in industrial filter systems.
Providing a clean environment is a problem which is currently drawing much attention; however, this problem has been facing manufacturers and other industrial shops for many years. Most every industrial plant and manufacturing facility, including steel mills, foundries, machine shops and other factories produce debris in the form of dust, slag, grinding dust, and the like. If this particulate matter is allowed to float freely into the atmosphere, the debris can add considerable pollutants to the air. Therefore, most plants include a mechanism whereby dirty air is passed through a filtration system. The debris carried by the air is trapped in the filtration system and the clean air is allowed to escape into the ambient. The dust and debris collected by the filter can then be disposed of properly.
A typical filtration mechanism which is used to collect debris is shown in FIG. 1. Air which has collected dirt and debris is allowed to pass into the filtration system, where the dirt can be trapped and collected. The clean air is then allowed to pass into the ambient. As shown in FIG. 1, a typical filtration device will include a dust collecting unit, indicated by the reference letter A. The dust collecting unit will typically be a large enclosure, PG,3 and may have dimensions as large as 40 feet by 120 feet, and be 60 feet in height.
As can be seen in FIG. 1, the dust collecting unit includes a plurality of filter bags suspended therein. The filter bag may typically be several inches in diameter, and up to 40 feet in length. The filter bag is typically constructed of a woven fabric material. As the dirty air passes through the filter bags, the debris is collected in the fabric. The clean air is then allowed to escape the baghouse, and the debris is maintained in the filter bag fabric.
The filter bags may be housed within the dust collecting unit in numerous ways. In one arrangement, a cell plate or tubesheet extends across the top of the dust collecting unit, or baghouse. A mesh wire cage is connected to the cell plate and hangs within the baghouse. The end of the mesh cage opposite the cell plate is suspended in air, hanging over the hopper. A filter bag is inserted over each cage, and extends the entire length of the cage. Dirty air enters the baghouse adjacent the hopper, and is allowed to circulate around the filter bags and cages. This type of system is known as an outside collection system, because the particulate matter trapped in the air is collected on the exterior, or outside surface of the filter bag. In some outside collection system units, the dirty air is also allowed to circulate through the interior of the cage and bag, and thus debris is collected on both the inside and outside surfaces of the bag. This type of arrangement is shown in FIG. 1.
A second manner in which the filter bags may be housed in the baghouse is through the use of a spring-tensioning mechanism. Instead of a cell plate near the top of the baghouse, the arrangement includes a plurality of beams which extend across the width of the dust collecting unit. Spaced along the beams are springs, which support the bags hanging from the beams. Opposite the beams, the baghouse includes a cell plate just above the hopper. The cell plate includes a thimble for each bag. The bottom of the bag is secured to the thimble, and thus the bag is maintained in a substantially vertical position.
In spring-tensioning systems, air enters the dust collecting unit near the hopper, and travels into the filter bags through the thimbles in the cell plate. As the air travels through the filter bag, the debris is captured and collected in the fabric of the bag. This type of collection unit is known as an inside collection unit, because the particulate matter is collected on the inside surface of the bag.
Known dust collecting units are typically either positive pressure units or negative pressure units. In a positive pressure baghouse, a fan pushes the dirty air through the baghouse. In a negative pressure baghouse, a fan located on the clean air side of the filters pulls the dirty air past the filter bags.
As the air passes the filter bags, the particulate matter and debris are captured in the fabric, and the clean air is allowed to escape. Thus, the atmosphere is not polluted with potentially harmful debris. However, over time, particle agglomeration can reduce the filtering capability of the filter bags. Particle agglomeration occurs when multiple particles join or are clustered together by surface tension to form larger particles. Such particles may be held together by moisture, static charge or particle architecture. Particle agglomeration is particularly prevalent in wet process dust collecting units. These units spray a water mist into the particulate-laden airstream. The moisture increases particle weight and causes particle agglomeration, allowing the heavier debris to drop out of the air.
However, the moistened dust and dirt can also collect on the filter cages, filter bags, and surrounding areas. When this occurs, particle agglomeration can cause corrosion and deterioration of the metal components of the dust collecting unit. The filter cage and cell plate are particularly susceptible to this corrosion. If the corrosion is extreme, large gaps or holes may be formed through which dirty air may pass. In these instances, the dirty air is not exposed to filtration and passes directly into the atmosphere.
Particle agglomeration can also reduce the effectiveness of the filter bag. If the filter bag becomes clogged, it will be unable to trap and collect the particulate from the passing air. Furthermore, particle agglomeration on the filter bag can cause blinding. Blinding is a fabric blockage caused by dirt or debris not being discharged, and can result in a reduced gas flow or increased pressure drop across the media.
Over time, the particle agglomeration matter solidifies, forming a hardened material known as "dustcake" or "hardcake". Hardcake bonds to the filter cage, filter bags, cell plate and surrounding areas. The hardcake can corrode the metal components, and deteriorate the fabric of the filter bag. Hardcake can accumulate on and around the cell plate and thimble, causing deterioration and corrosion. This weakens and reduces the effectiveness of the seal between the filter bag and the cell plate, and thus can also reduce the effectiveness of the filtering capabilities of the unit. Furthermore, excessive amounts of hardcake can make removal of the filter bag and cage difficult.
To limit the deteriorative effects of the particulate matter collected in the baghouse, it can be beneficial to clean the system. One known method of removing hardcake material is by repeatedly striking the material with a hammer or similar instrument. Sandblasters have also been used to clean hardcake from dust collecting units. Using a hammer or similar instrument, however, can cause additional harm to the cage, cell plate and other areas being cleaned. Furthermore, if the hardcake material has caused corrosion to the surrounding metallic components, striking them with a hammer can cause even greater damage. Thus, it is beneficial to loosen and remove hardcake material without further damaging the metallic components to which the hardcake material is attached.
In addition to hammers and sandblasters, blowpipes have been used to clean debris from filter cages and bags. As shown in FIG. 2, a blowpipe extends across the opening of several successive filter cages, substantially orthogonal to the longitudinal axis of each filter cage and bag. The blowpipe includes several orifices therein, one corresponding to each cage. Pressurized air is conveyed through the blowpipe and is allowed to escape out the orifices and into each cage. The blowpipe is designed to supply pressurized air to the filter cage and bag, thus removing the debris from the bag. Some blowpipe units include a nozzle which extends from each orifice up to the opening of the cage. Some cage units additionally include a venturi device in the cage adjacent the cell pipe. A venturi is typically a conically-shaped device which creates a negative pressure at the top of the venturi to help pull additional air down into the filter cage and bag. In these known blowpipe systems, several pulses of pressurized air may be directed into the filter cage to clean the debris from the cage and bag.
These known cleaning arrangement are inadequate to fully clean the filter cage and filter bag for several reasons. First, the pressure of the air in the blowpipe is greatest near the source of pressurized air, and weakest opposite the source. The air being dispersed into the cages far from the air source is thus of a lower pressure than the air in the blowpipe near the air source. The air under less pressure may be ineffective at removing dirt and debris, and especially dustcake, from the filter cages and bags which are further removed from the source of pressurized air.
Second, the known systems are ineffective at cleaning the entire length of the filter cage and bag. A typical filter cage and bag unit may be 40 feet in length. The burst or pulse of air shot into one end of the cage may clean debris from a longitudinal portion of the bag near the blowpipe, but not near the end of the bag opposite the blowpipe. As the air flows down the length of the cage and bag, its pressure is reduced, and it is ineffective at cleaning the bottom portions of the bag. Thus, these portions of the filter bag and cage remain clogged with debris.
Third, known blowpipe systems are stationary, and cannot be used to clean other areas of the dust collecting unit. For example, particle agglomeration may accumulate near the thimble area and on the cell plate, on and around doors, vents, ducts, dampers, fans, hoppers, tensioning assemblies, and other areas. The known blowpipe systems are directed only into the filter cage and bag, and thus cannot be used to clean these areas.
The known blowpipe systems are particularly ineffective at cleaning the surrounding areas of a dust collecting unit utilizing a spring-tensioning mechanism of suspending the filter bags. A filter bag fully laden with slag, dust and particle agglomeration can cause damage to the tensioning system. The weight of the particle agglomeration collected on the bag can be in excess of 175 pounds. This excess weight can damage the spring supporting the bag. Thus, a clean bag reduces the tension on the spring, and extends its life. Furthermore, hardcake can collect on and around the spring-tensioning unit. This can restrict the free movement of the system. Removing the hardcake material from around the spring frees the tensioning unit, and further extends its life.
In baghouses where the filter cage and bag are attached to a top cell plate, hardcake material will often collect on the cell plate, restricting access to both the filter cage and the filter bag. Thus, when the filter bag is full, it may be difficult to remove the bag from the dust collecting unit. It is therefore advantageous to be able to remove hardcake material from the cell plate adjacent the connection to the filter cage and filter bag. Furthermore, if the filter cage and bag are too heavy to remove from the cell plate, or are too deteriorated for further use, it may be beneficial to be able to remove them from the cell plate.
Accordingly, an object of the present invention is to provide a cleaning device which is able to clean debris and dirt from the entire length of a filter cage and filter bag.
Another object of the present invention is to provide a cleaning device which is able to break hardcake material free from a filter cage, filter bag, and surrounding areas of a dust collecting unit.
A further object of the present invention is to provide a cleaning device which is portable, such that it may be used to clean surrounding areas of a dust collecting unit, such as the cell plate, thimbles, doors, ducts, and the like.
Yet another object of the present invention is to provide a cleaning device which cleans both the inside and the outside surfaces of a filter bag.
Yet another object of the present invention is to provide a cleaning device which aids in the removal of a filter cage and filter bag from the cell plate when the bag is too heavy for normal removal.
These and other objects are attained by a reducer cannon cleaning device. The cleaning device of the present invention is portable, and can be used by a single individual. The device includes a handle which is substantially hollow. Attached to the handle is a source of pressurized air. Opposite the pressurized air, connected to the handle, is a substantially hollow conduit. By controlling a ball valve located on the handle, pressurized air may enter the hollow handle and flow into the conduit.
Mounted to the conduit, the cleaning device includes a diaphragm, connected to a solenoid. The solenoid is connected to a trigger mounted on the handle. A user can depress the trigger, activating the solenoid, and thereby positioning the diaphragm in an open or closed position. In a closed position, the pressurized air is prevented from flowing out of the conduit. In an open position, the air is allowed to exit the conduit.
Attached to the distal end of the conduit is a plate. The plate is a substantially circular disc, and is designed to fit over the hole of a filter cage and filter bag. A gasket is positioned between the plate and the cell plate or tubesheet. The gasket is a two-part gasket, having a substantially rigid outer surface and a pliable inner core. The gasket forms to the shape of the ceil plate, filter cage and filter bag, such that air does not escape adjacent the cell plate.
In use, the cleaning device is positioned about a filter cage and filter bag such that the plate covers the opening to the cage. The user can depress the trigger, thereby allowing pressurized air to flow through the cleaning device and out the end of the conduit. The gasket ensures that air does not escape around the cell plate. The air may be released in short pulses, or in longer continuous blasts.
Because the reducer cannon cleaning device is portable, it can also be used to clean areas adjacent the filter cage and filter bag. The cleaning device can be pointed at areas desired to be cleaned, such as cell plates, spring-tensioning systems, thimbles, ducts and the like. Pulses of air can be directed towards particle agglomeration at these locations, loosening hardcake and freeing dirt and debris.
The present invention also includes a series of attachments for use when cleaning a filter cage and bag. One attachment is a substantially cylindrical, hollow pipe. A plurality of holes are placed in the pipe at pre-determined locations and pre-determined angles. The pipe is attached to the distal end of the conduit, and can be placed inside the filter cage and bag. Air traveling through the conduit enters the attachment and escapes through the holes.
A second attachment includes a substantially cylindrical, hollow adapter tube. In this attachment, the tube does not include holes along the longitudinal sides, but instead includes a cap on its distal end. The cap has a plurality of holes therein, which can be positioned and angled as desired.
A third attachment for the cleaning device includes a substantially shortened cylindrical compact nozzle which can be attached to the conduit. At the distal end of the nozzle is a bell reducer, which directs and focuses the air as it leaves the attachment.
A fourth attachment which can be used in conjunction with the present invention is a cage crushing device. When hardcake and dustcake have built up around the cell plate and cage, it may be desired to remove the cage from the cell plate. A mechanical hand, including spaced apart mechanical fingers, can be attached to the cleaning device of the present invention. The mechanical hand is placed about the top of the filter cage. The user actuates the trigger on the cleaning device, thus supplying air to the mechanical hand. The fingers on the mechanical hand contract in response to the flow of air, and thereby crush the top of the filter cage. Once removed from the cell plate, the filter cage and bag are dropped from the baghouse into the hopper.